Airplane wing spar



.181112, 1934. RG M|L. ER f A' 1,942,391

AIRPLANE WING SPAR Filed April 2a, 1932' 2 sheets-sheet 1 INVENTOR l ,Fay Mil/fl' BY- Mfr@ ATToRNEYs Jan. 2, 1934. R. G. MILLER l 1,942,391

' AIRPLANE WING'SPAR f Filed April 2s, 1932 zrsne'ets-sheet 2 L 'Patented Jan. 2,1934

AIRPLANE WING SPAR Royl G. Miller, Farmingdale, N. Y., 'assignor to Curtiss Aeroplane &

Motor Company, Inc.,

Bualo, N. Y., a corporation of New York v Application April 26, 1932. serial No. 607,545"

Claims.

This invention relates in general to airplane construction and more particularly to a construction of airplane wing spars.

The object of the invention is to provide an 5 airplane wing which may be easily assembled to the end that it will be properly braced when assembled. l

Another object is to provide an inherently braced wing spar so that the truss construction l0 may be assembled without the use of separate gussets.

Another object is to provide a truss assembly of hollow chord members which may be braced by 'tubular diagonals and that the necessary connections vmay be made by single rivet patterns,

vwhich rivets may be applied by the use of ordinary squeeze tools. Another Objectis to provide such a construction in respect to the truss members that the terminal strength and the joint xity to the chord members will be improved.

Another object is to provide such a construction that will minimize the'tend'ency of failureV by twisting or locally crinkling.

Another object is to provide suchv a construction that will so eliminate the conventional multiplicity of parts asto considerably reduce the weight of the wing construction. y Another object is to provide such a-wing-con'- 23o/struction wherein the intersection of 'the wing spar members and the wing spar will be such as to equalize the stress distribution induced in the chord members through -beam action. With the foregoing and other objects in view,

35 the invention consists in the details of construction and the combination of parts hereinafter set forth in the following specication'and appended claims, certain embodiments thereof being illustrated in the accompanying drawings, in which:

Figure 1 is a view in perspectiveof the-wing spar showing its intersection with onepf the rib members;

15 Figure 2 is an enlarged view in front'elevation of thewing spar; y

Figure 3 is a detailed view showing the manner in which the tubular diagonal ltruss members are connected to the frame chord member of the spar;

Figure 4 is a view in section taken along linec 4 4 of Figure 3; s

Figure 5 is aview similar toj Figure 4 showing a modification of the form shown therein;

Figure 6 is asimilar viewshowing another modified form;

.Figure 7 is asimilar view showing another modified form; i

Figure `8 is a similar View showing another modified form;

Figure' 9 is a View in side elevation of a modified 60 l form of tension diagonal truss member;

'Figure 10 is a view in front elevation of thatI shown inY Figure 9;v

Figure 11 is a View in section taken along line 11-11 of Figure 9; 1

Figure 12 is a View in cross-section taken through amodiedform of diagonal truss mem- 1 ber;

Figure 13 is a view incross-section of another modied form of diagonal truss member;

Figure 14 is a View in front elevation showing a pair of diagonal truss members, such as shown in Figures 9 and 10, and their relative position to the spar chord, which latter is shown in dotted lines;

Figure 15 is a view in section taken along line 15-15 of Figure 3;

Figure 16 is a view taken through the spar chord'and the overlapping terminals of two adjacent diagonal truss members and also showing a' series of rivets and theoperating members of a suitable device for squeezing the rivets to ef fect the connection of these adjacent members.

Referring more particularly to the drawings, and especially/to Figure 4, the airplane wing spar consists primarily of a U-strip 1 and acap strip 2, which is riveted to the U-strip by rivets 3 and 4 to form theupper and lower frame chord members indicated generally at 5 and 6, respectively, in Figure 2. A series of tubular diagonal members, such as shown in Figure 2, at '7, 8, 9, 10, etc., are connected to each other and to therupper and lower frame chord members of the spar'to constitute a Warren truss'for the spar. 'o

These tubular members have their ends iiattened and split so as to saddle the U-strip of the 'spar frame chord member and one of the diagonal terminals is split so as to be wider than the terminaly of the adjacent diagonal so thatit may saddle the same. In. this manner a single .rivet patternmaybeused for `the connection of the two adjacent terminals to each other and the spar, U-strip. This rivet pattern is shown in de, J

tail in Figures 3 and 4. f I have found it prefer- 105 able to enlarge the split terminal of the tension diagonals so that they will fit snugly over the vx" terminal of the adjacent compression diagonal as ithe latter is iitted snuglyover the U-strip and -Y therefore this general scheme-is carried through-f l out the entirel Warren truss. For purposes of A illustration, in Figure 3," the diagonal 10 may be referred to as a tension diagonal and diagonal 9 as a compression member. By references to 5 Figures 3 and 4, it will then be seen that the split terminal 9' of the compression diagonal i'lts snugly about the U-strip 1 'and that the split terminal lfof the tension diagonal 10 fits snugly about the terminal 9. v1 'Ihe'v sequence of the assembly of the construction is preferably, as follows: The tubular diagonals are arranged and heldin ajig and the upper and lower U-strips 1 ad,1' are then placed and riveted to Athe tubular diagonals after they have been placed in the particular relationship above described and illustrated in' Figures 3 and 4. While held in such position a` series of rivets may then be applied by the use of ordinary, squeeze tools so as to securely fasten the .I two adjacent diagonal terminalsto each other and* to the U-strip." An illustration of such a rivet pattern shown in Figures 3 and 4 but may be modied to suit any particular requirements.` For purposes of identification these rivets generally are indicated at 11. V'Ihe next procedure is to secure the cap strips to the U-strips so as to form the frame chord member ofthe spar. The I U-strips are preferably formed so -as to provide anges 12 and 13, to provide for easy application of the rivets 3 and 4 for securing the cap strip thereto. The lcap strip may assume various actual forms as exempliiied in the modications shown in Figures 5 to 8, inclusive.- In each instance it is considered preferable to so form the cap strip that they outer edges will be rounded by such means as curving the -ends downwardly and inwardly, as shownffor example, in Figure 4, at 14-15. In this connection, it may be as'- j sumed that the application o'f the rivets 3 and- 4, as shown in Figure 4, may assume any pargicular pattern as strength requirements may call This construction, aiording as it does the use of single rivet patterns for the joining of the terminals of both diagonals to each'U-strip o f the spar chord member, does away with the use of separate gussets found in the conventional construction without in any way lessening the 'strength of the spar construction. Thismakes for not only simple construction but rapid assembly as will be appreciated by the above description of the sequence o1' assembly and also lessens the weight of the construction to' a very appreciable degree by the elimination of gusset plates. The

use .of seamless hollow chordifmembers also makes for lightness. of constructin and'reliable strength requirements. The manner of assembly of the spar further makes for improved terminal strength and joint xity to improve the strength o f the chord members. It is also o1' importance that the use of hollow members eliminates a tendency to fail by twisting and further the use of open edges in each chord-member and the fact that these edges-are bent at 14 and 15 towards its gravity axis prevents local crinkling. Y

All of the extremes of the contour are curvedA in section ,tcincrease the strength of the assemfV bly and byithis statement I havel reference to the curvature of the closed end of the -U`strip. .-'the curved portion of the cap strip in alignment with the curved bottom of the U- strip, and also the curvature of the upper ends of the cap strip; As shown in Figures 5 to 8, inclusive', several ternate shapes of chord'members may be'used to iit certain aerofeils Vand to'employ extruded In each instance-however, such as' in Figures l5, 6 and 8, the same principle is employed as regardsthe construction of the extremes of the contour, so that it is curved in section to increasel the strength and by thisA I have reference 1to the fact that the bottom of the U-strip isv curved and the portion of the cap strip in alignment therewith and the ends of the cap strip are both also accordingly curved. A slightly modied form is shown in Figure 7, in which the bottom portion of the U-strip may be not only curved but enlarged in wall thickness at 16, the cap strip 2 instead of being curved may be its wall thickness, enlarged at 17 in alignment with the bottom of the U-strip and the extremities of the cap strips 18 ,and 19 and the extremities of the U-strip japgseo and 21 may au have their wan thickness ,enlargedy As shown in Figure' 1, the intersection of theweb members is preferably excentric to the grav-v ity axis of the chord as indicated at 32 so as to have a tendency to equalize the stress distribution induced inthe chordl members through beam action. The wing rib maycompriseupper and'low-A er chord members22 and23with suitable diagonal truss members 24. The nose plate of the wing is indicated at 25. The wing ribs may be each provided with curved brackets, such as 26, so as to releasably engage and holdin place the frame chord membersof the wing spar. This figure, while not drawn to anexact -scale generally represents the relationship of the point of intersection of the spar with the rib and the nose strip, so as to indicate generally the excentric of the point of intersection with relation Ato the curved axis of the chord. e

While I have illustratedand described all of the diagonals of the Warren truss for the wing spar as tubular members, vI may employ mem- 7" bers of different construction. However, in ref- 'rerence to -any change from the construction, shown and described, I would bpreferably limit such change so that'` the Ncompression members would remain 'as shownand described and arrange the tension diagonals so that they would 120 be of opensection, in order to possibly facilitate assembly. In carrying out this change Figures 9 and 10 `'show-twoarbitrary sections which I may employ.

Thus the tension diagonal 27 is formed so that 125 its cross-section will have severalcgnvolutions as a strengthening expedient, as shown in Figures 9 and 11. Figures 12` and 13 merely show other cross-sections which may be employed in place of thatvshown in Figure 11. The .truss member 27 isprovi ed with a series of apertures '28m-ranged in any arbitrary pattern, which bears` some resemblance to the pattern shown in Figure 3. In using this type of diagonal I propose to only use/'them as tension diagonals so that the 135 diagonal 9, as shown in Figures 3 and 4, would remain the same and retain the overlapping relationsliip with the U-strip as shown in Figure 4. When thisform of tension diagonal is used they will be used in duplicate, as shown in Figure 14, and eachfattened terminal will overlap a .terminal of the adjacent compression diagonal.

Figure 15 is a cross-section through the tubular diagonal looking towards the split terminal and illustrates t e fact' that while theterminal `10' i is split and attened the upper? 'and lower walls are left substantially straight soas to provide for soy able because of its strength and eiciency. In the modificationshown in Figure 3, both the compression and tension diagonals are formed in the manner shown in Figure 15, and even when tension diagonals of the type indicated in Figures 9 to 14 inclusive are used, the compression diagonals remain the same as shown in Figure 3 and have the particular cross-section shown in Figure 15. The walls 10a of the tension diagonal tube 10 are carried through straight and are coplanar with the palmed end.

I have hereinbefore referred to the fact that the particular construction and arrangement of the trussmembers and the U-strip of the spar chord makes it a simple matter to produce the rivet pattern for the connection of the terminals of the diagonal truss members to each other and to the U-strip. A preferred method is illus-- trated in Figure 16, in which are shown lthe U-strip 1, the terminals 9 and 10' of the compression and tension diagonals, all placed together with rivet holes in alignment and with a series of rivets 1l extending therefrom ready to be squeezed. There is also shown in this figure a bar of metallic material 29 which may be inserted in the U-strip, so as to provide for a backing for the inward and opposed plungerv action of the two opposed plungers 30 and 31 against the rivets. It will be seen that this plunger action will not in any manner destroy the contour of the U-strip, nor in any way damage the diagonal terminals or the U-strips. These plungers may be of the ordinary hydraulic or mechanical press type.

I claim:

1. A truss construction comprising a pair of U-shaped beams With cap strips riveted to and covering the open end thereof, a plurality of diagonal bracing elements extending between said beams and connected directly to each other and to said beams, each of said connections beand to said beams, each of said connections being adapted to be eiected by a single rivet pattern, said beam and cap strip having the extremities of their contours curved.

3. An airplane wing spar comprising a pair of U-shaped chord members having parallel sides, a plurality of tension and compression bracing elements extending therebetween and connected directly to each other and to said chord members at points excentric to the gravity axis of the l spar chord.v

4. An airplane wing spar comprising a pair of U-shaped chord members having parallel sides, a plurality of tension and compression bracing elements extending therebetween and connected directly to each other and to said chord members, each of said connections being adapted to be effected by a single group of rivets at points excentric to the gravity axis of the spar chord.

5. An airplane wing spar comprising a pair of U-shaped chord members having parallel sides, a plurality of tension and compression bracing elements extending therebetween and connected directly to each other and to said chord members, the terminals of said diagonals being arranged to overlap said chord members and said tension elements being arranged to overlap said compression elements, each of said connections being effected by a single'group of rivets at points excentric to the gravity axis of the spar chord, each of said chord members being provided with a cap strip.

. ROY G. NUILER. 

